Conventionally, there is known an internal combustion engine that ignites fuel air mixture more forcefully than a spark discharge caused by momentary application of a high voltage pulse. With this kind of internal combustion engine, it is possible to stably ignite lean fuel air mixture in comparison with a case in which the fuel air mixture is ignited by the spark discharge. For example, Japanese Unexamined Patent Application, Publication No. 2010-96112 and Japanese Unexamined Patent Application, Publication No. 2011-7157 disclose internal combustion engines that ignite fuel air mixture by way of high intensity plasma.
Japanese Unexamined Patent Application, Publication No. 2010-96112 discloses a plasma ignition device that supplies a large current stored in a capacitor to an ignition plug immediately after application of a high voltage from an ignition coil. While, on the other hand, Japanese Unexamined Patent Application, Publication No. 2011-7157 discloses a spark ignition internal combustion engine that supplies a boosted alternating voltage to an ignition plug.